With a high integration of semiconductor devices and a reduction in chip size, a miniaturization of wiring and a multi-layered wiring have been developed. In the semiconductor device having a multilayer wiring structure, a propagation delay of a signal in the wiring is proportional to a product of a wire resistance R and a capacitance C between wires (RC product). Thus, in order to improve a propagation speed of the signal, it is considered to be effective to reduce the wire resistance and reduce the capacitance between wires.
In order to reduce the wire resistance R, a technique of using a low-resistivity copper as a wiring material has been put to practical use. Recently, a copper wiring is generally formed by a damascene process. When forming the copper wiring by the damascene process, the inner surface of a via hole or a wiring groove is coated with a barrier film in order to prevent a diffusion of copper atoms into an insulating film, or to prevent a diffusion of oxygen into the copper wiring from the insulating film.
As a material of the barrier film, a high melting point metal such as tantalum or tungsten has been used, but the high melting point metal has a resistivity higher than that of copper. The miniaturization of the wiring increases the proportion of the barrier film with respect to the copper wiring, making the barrier film a major factor to increase the wire resistance. Thus, in the fine multilayer wiring structure, in order to suppress the increase in the wire resistance, it is required to make the barrier film as thin as possible.
From this point of view, in recent years, as a barrier film, a manganese-containing barrier film such as manganese oxide has been attracting attention. Since the manganese-containing barrier film can be formed in a self-aligned manner by performing an annealing treatment after a thin film of manganese or an alloy of manganese is formed by a method such as a sputtering, there is an advantage that the thickness of the barrier film can be thin (e.g., Japanese Patent Application Publication No. 2005-277390). In addition, technology for forming the manganese-containing barrier film by a thermal chemical vapor deposition (CVD) method has also been proposed (e.g., Japanese Patent Application Publication No. 2009-16782).
Meanwhile, the capacitance C between wires can be reduced by forming an interlayer insulating film by using a low dielectric constant material. Further, by using the low dielectric constant material, it is possible to prevent crosstalks between wires. From this point of view, as the interlayer insulating film, a low dielectric constant film (low-k film) has been used. Moreover, the development of a porous low dielectric constant film (porous low-k film) to further reduce a parasitic capacitance by dispersing pores in the low dielectric constant film has been being pursued.
In a case where the manganese-containing barrier film is formed by a CVD method, since the manganese-containing barrier film is hardly deposited on the low dielectric constant film, there is a problem such that it is difficult to form a film thick enough to make it function as a barrier. Further, if the manganese-containing barrier film is formed on the porous low-k film by a CVD method, manganese may enter into the pores of the porous low-k film, thereby causing the diffusion of copper atoms from the copper wiring.